A Multicomponent Diffusion in the Presence of Reaction

The binary molecular diffusion coefficient, DAB, can be derived from the kinetic gas theory. A more accurate empirical correlation is given by  

In general, however, reaction is accompanied with expansion or contraction  

Hence the so-called effective binary diffusion coefficient, D m is introduced. The latter is defined as  

For ideal gases an expression for the effective binary diffusion coefficient, D m, as a function of the binary diffusion coefficient, DA], can be derived as in this case the Stefan-Maxwell equation holds  

Solving 7.A8 for dC /dz and equating the result to the right-hand side of 7.A9 leads to  

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